1. Field of the Invention
The present invention relates to a finder field frame switcher for cameras, and more particularly, to a finder field frame switcher in the advanced photo system having a plurality of image plane formats.
2. Description of the Prior Art
In the advanced photo system (hereinafter, referred to as APS) that have been commercialized in recent years, the image size format can be selected from among the following three types: a wide type (hereinafter, referred to as "H type") with a length-to-width ratio of 9:16; a standard type (hereinafter, referred to as "C type") with a length-to-width ratio of 2:3 in which, compared to the H type, the length is the same and the width is shorter; and a panorama type (hereinafter, referred to as "P type") with a length-to-width ratio of 1:3 in which, compared to the H type, the width is the same and the length is shorter.
When an image size is selected by the user, it is necessary to switch the finder field frame. A conventional camera having a finder field frame switcher is arranged, for example, as shown in FIG. 1. According to FIG. 1, a luminous flux A emanating from a subject and entering a camera 1 through a taking lens 2 is reflected at a reflecting mirror 3 and imaged at a focusing screen 4.
In photographing, since the reflecting mirror 3 rotates so as to retreat to the vicinity of the focusing screen 4 and a shutter 12 is released for a predetermined time, the luminous flux A reaches a film 9 to expose the film 9. In the APS, since image size information is recorded onto the film 9 by magnetic writing by use of a magnetic head (not shown) or by identification mark recording by use of a light emitting device (not shown), even if the film 9 is not shielded from light according to the image size format, the image size is decided based on the recorded image size information and printing onto photographic paper is performed.
On the other hand, in another system, for example, in a 135-type system, to switch between the standard image plane and the panoramic image plane, a field frame switching mechanism is necessarily provided in the front or in the rear of the shutter 12.
In the rear of the focusing screen 4 on the optical path of the luminous flux A, a fixed field frame 5 having an H-type field frame and light interrupting wings 6 being rotatable are provided so that the light interrupting wings 6 rotate to switch between the H-type field frame and a P-type field frame. In the figure, the P-type field frame is selected when the light interrupting wings 6 are lying. The light interrupting wings 6 are also provided in positions parallel to the plane of the figure so as to switch between the H-type field frame and a C-type field frame. The image formed at the focusing screen 4 is reflected at a pentagonal Dach mirror 11 and enlarged by an eyepiece 8 so that the user can confirm the image of the desired field frame.
In order to automatically adjust exposure, a part (luminous flux A2) of the luminous flux A having been imaged at the focusing screen 4 is captured by the automatic exposure (AE) sensor 10 to detect brightness. Further describing with reference to a detailed view shown in FIG. 2, the focusing screen 4 and the AE sensor 10 are disposed so that the luminous flux A2 to be captured by the AE sensor 10 is not interrupted by the light interrupting wing 6 when the light interrupting wing 6 is standing upright to form the H-type or the C-type field frame.
Subsequently, another conventional example will be described. As shown in FIG. 3, a finder field 21 which can be viewed by the user includes an image display portion 22 having an image plane corresponding to the H type, and information display portions 25a and 25b. When the C-type or the P-type field frame is selected, the focusing screen 4 (see subsequently-described FIG. 4) is shielded from light, so that a field 23 or 24 is displayed on the image display portion 22.
On the information display portions 25a and 25b, information such as the aperture value, the shutter speed, the flash indicator and the in-focus indicator is displayed so that the user is informed of the information.
A method of displaying information on the information display portions 25a and 25b will be described with reference to FIG. 4. In FIG. 4, the fixed field frame 5 and light interrupting wings 6a and 6b are disposed above the focusing screen 4 in the structure of the camera 1 similar to that of FIG. 1. The light interrupting wings 6a and 6b are rotatable between a position that covers a field limiting portion 5a of the fixed field frame 5 and a position that is retreated from the field limiting portion 5a so that the field frame can be switched between the P type and the H type.
At a side of the focusing screen 4, a display member 32 such as a transmission-type liquid crystal panel is attached to the camera 1 by a fixing member 34. A luminous flux B from a backlight 33 is reflected at a mirror 31 to reach the eyepiece 8 together with the luminous flux A1 of the image on the focusing screen 4, so that information is displayed on the information display portion 25a in a lower part of the finder field 21 in the previously-described FIG. 3.
Moreover, by a similar structure, switching between the C-type field frame and the H-type field frame can be performed by the light interrupting wings 6a and 6b. Further, by a similar structure, information can be displayed on the information display portion 25b in a side part of the finder field 21.
In the arrangement in which the AE sensor 10 and the display member 32 are disposed in the vicinity of the focusing screen 4 as shown in FIGS. 2 and 4, the light interrupting wings 6a and 6b are disposed in positions that do not interrupt the luminous fluxes A2 and B since the luminous fluxes A2 and B used for obtaining information necessary for photographing cannot perform their functions if they are interrupted by the light interrupting wings 6a and 6b. However, such an arrangement requires a large space (L1 and L2 of FIGS. 2 and 4) in the rear of the focusing screen 4 on the optical path of the luminous flux A from the subject. This has been an obstacle to size reduction of the camera.